1. Field of the Invention
The present invention relates to a pulse radar system using a millimeter wave band or a quasi-millimeter wave band, and particularly to a pulse radar system having improvements in distance resolution with respect to a reflective wave from objects in a short distance.
2. Description of the Related Art
Recently, a pulse radar system is used with the purpose of collision avoidance or auto clews. The round-trip distance to an object can be found by multiplying the time that elapses between the radiation of a transmission pulse and the receipt of a reception pulse wave reflected from the object, by light velocity. Consequently, the pulse radar system is intended for calculating the distance to the object by measuring the time that elapses between the radiation of the transmission pulse wave and the receipt of the reception pulse wave from the object.
In this pulse radar system, the transmission pulse wave is radiated, followed by preparation for receiving the reception pulse wave reflected from the object in a short distance. The pulse radar system with the purpose of collision avoidance or auto clews demands exact detection of the positions of objects in a wide range of from tens of centimeters to tens of meters.
When detecting the positions of two or more objects adjacent to each other, the reflected waves from the different objects reach the pulse radar system at substantially the same time. Therefore, in the conventional method for detecting the positions of different objects, the pulse width of a transmission pulse wave is reduced so as to eliminate overlapping between reception pulse waves from the different objects, thereby increasing distance resolution between those objects (for example, refer to Japanese Unexamined Patent Publication No. 6-249943).